Flow control device



June 23, 1959 DAHL ETAL 2,891,578

FLOW CONTROL DEVICE Filed Jan; 9, 1956 Fig.3

/ I I I FLOW -GPM 0 so I00 1 20 PRESSURE DROP PSI hz EJ 2'? far" 5,Passer P. 04/14 7 Ho WARD L. ERIC/ 80 United States FLOW CONTROL DEVICEApplication January 9, 1956, Serial No. 558,088

1 Claim. (Cl. 138-45) This invention relates to improvements in flowcontrol devices for maintaining a substantially constant rate of fluidflow over a wide range of pressure variations.

Flow control devices in the forms of resilient annuluses reactingagainst a seat have come into quite common use for controlling the flowof liquids and particularly water at household pressures. While suchflow control devices have gained a wide acceptance, at low pressure theyhave provided too much restriction to flow, so that the desired flowrate was not maintained when the water supply pressure became too low.

In carrying out our invention we remedy this deficiency in the controlof the flow at the low pressure conditions by providing a taper in theorifice of the flow control device, tapering outwardly from the upstreamto downstream side thereof at a relatively flat angle.

. It is accordingly a principal object of our invention to provide aresilient flow control device so constructed and arranged as to improvethe flow characteristics of the device, particularly at the point wherethe pressure passing through the washer or flow control device may dropoff.

A further object of the invention is to provide a flo-w control devicein the form of a resilient annulus in which the flow at low pressureconditions is made more uniform than formerly with a decreased drop offin flow at such pressure conditions.

A further object of the invention is to provide a more accurateresilient annular flow control device in which the contour of the seatfor the device has no effect on the flow control characteristics ofdevice, and in which the efiiciency of the control of the flow isincreased by tapering the orifice of the flow control device outwardlyfrom the inlet to the outlet end thereof.

These and other objects of the invention will appear from time to timeas the following specification proceeds and with reference to theaccompanying drawings wherein:

Figure 1 is a cross-sectional view taken through a fluid flowpassageway, showing a flow control device constructed in accordance withour invention in the passageway with no fluid pressure on the flowcontrol device;

Figure 2 is a plan view of the flow control device looking at the devicefrom the downstream side thereof;

Figure 3 is an enlarged sectional view taken through the flow controldevice; and

Figure 4 is a graph showing comparative curves of two flow controldevices of the same general design, one of which has a tapered orificein accordance with the teachings of the present invention, and the otherof which has a non-tapered orifice of a diameter equal to the smallestdiameter of the tapered orifice.

In the embodiment of the invention illustrated in the drawing, we haveshown in Figure 1 a cross-section taken through a fitting or hollowhousing of a type adapted to be connected in a fluid conduit or theinlet or outlet of a valve and the like. The housing 16 is internallythreaded at its inlet end as indicated by reference character 11 forthreaded engagement with a fitting or pipe, and is externally threadedat its discharge end as indicated by atnt 2,891,578 Patented June 23,1959 reference character 12, to be threadedly received withi a valvebody or fitting or the like.

The interior wall of the housing 10 on the downstream side of thethreaded portion thereof forms a flow passage 13 for fluid, such aswater,'and is shown as havinga shoulder 14 therein abutted by a rigidannulus or collar 15 seated against the shoulder 14 and'having a flatseating surface 16 forming a shoulder or seat in the passageway 13against which an annular flow control device 17 reacts, to control theflow of fluid through the housing 10 and to maintain the flow relativelyuniform over a wide range of pressure variations.

The flow control device 17 controls the flow of fluid by flexing orbending inwardly upon increases in pressure to reduce thecross-sectional area of a central orifice 19 leading therethrough, asthe pressure increases, on the same general principles as are disclosedin Patent No. 2,454,929, which issued to L. A. Kempton on November 30,1948. I The particular flow control device 17 embodies the improvementsshown and described in a copending application Serial No. 389,210entitled, Flow Control Structure, filed by Robert R. Dahl on October 30,1953, now Patent No. 2,775,984. v

The flow control device may be made from a resilient or elasticmaterial, such as rubber or one ofthe well known substitutes for rubber,such as neoprene and the like, of such elasticity as to be readilyflexible in a downstream direction upon increases in pressure of thefluid acting on the upstream face thereof and to return to its initialposition upon reductions in pressure thereon.

Spaced in an upstream direction from the upstream face of the flowcontrol device 17 is a retaining ring 20' which may be a press fittedinsert or the like. The retaining ring 20 is spaced from the flowcontrol device 17 a sufiicient distance to accommodate some freedom ofmovement of the flow control device within the housing 10, butsufliciently close to said flow control device to maintain the flowcontrol device in position to engage its seat upon the flow of fluidthrough the housing.

The flow control device 17 is shown as having a flat face 21 on theupstream side thereof converging in a uniform curve into the orifice 19leading through the device and providing a uniformly smooth orifice forall degrees of flexure of the flow control device. The flow controldevice also has an outer wall 22 loosely fitting within the passageway13 in the interior of the housing 10 and a downstream face 23 seatingagainst the flat seating surface 16 adjacent its periphery and contouredinwardly in the form of a flat angled frustum of a cone as indicated byreference character 24. The frustoconical recess surface 24 terminatesinto an annular surface 25, shown in Figure 1 as being parallel to theface of the seat 16 and terminating at the outlet end of the orifice 19in the form of a clean sharp edge.

The diameter of the orifice 19 may be varied for varying flow conditionsprovided it is not larger in diameter than the diameter of thepassageway through the collar 15. As herein shown, the orifice 19 tapersoutwardly from the inlet to the outlet end thereof at an angle which isherein shown as being four degrees, but the taper included may be ofvarious other angles, best results usually occurring when the angle isbetween two degrees and six degrees, with lesser improvements overnontapered orifices occurring when the angle of the taper is between oneand two and between six and nine degrees.

In Figure 4 we have shown comparative curves for two similar flowcontrols, curve A being a flow performance curve of a flow controldevice like that shown in Figure 1 except that the orifice has no taper.

Curve B, however, is a flow performance curve of a flow control devicehaving an orifice tapered from the 3 inlet to the outlet end thereof atan included angle of four degrees.

It may be seen from a comparison of curves A and B that the fiow controlperformance of the flow washer withouta tapered orifice indicated bycurve A is much poorer than that of the flow washer indicated by curveB, in which the washer tested has a four degree tapered orifice. Curve Ashows that the flow washer does not come into its rated flow range untilthe pressure drop across the washer is seventeen pounds per square inch.The fiow from seventeen pounds to sixty pounds is then substantiallyuniform until the pressure drop across the orifice through the washerflow control device reaches sixty pounds per square inch, at which timethe flow gradually drops off.

In curve B taken from tests made of a flow washer of the same design asthe flow washer from which the curve A was taken, but having a taperedorifice, the taper of which is four degrees, the flow washer reaches itsrated flow at a pressure drop of substantially six pounds per squareinch and the flow is maintained substantially uniform until the pressuredrop reaches eighty pounds per square inch, at which time the flowgradually drops olf.

It will be noted from a comparison of curves A and B that the taper hasthe effect of reducing the rated flow rate. However, the tapered orificecould be made larger to increase the rated flow rate, and this wouldfurther improve the flow at low pressures.

The difference in the pressure drops at which the respective flowwashers reach their rated fiow rates may appear small in comparison tothe total pressure drop range, but the improvement afiorded by the taperoccurs at a critical place and has made the difference between failureand success in providing flow control for household appliances used inplaces where the pressure of the water supply may become low.

It may be seen from the foregoing that we have provided a simple form offlow control device, which by the simple expedient of tapering the flowcontrol orifice through the device attains far superior flowcharacteristic over former flow control devices in which there is notaper to the wall of the orifice, and that this superiority in flowcontrol has enabled the flow control to conform to flow controlrequirements that could not be met by the flow control of curve A.

It will be understood that modifications and variations of the presentinvention may be effected without departing from the spirit and scope ofthe novel concepts thereof.

We claim as our invention:

In a fiow control device, a housing having a passageway leadingtherethrough, a seat in said passageway having a flow passageway leadingtherethrough, a resilient disc-like annular flow control device having agenerally concave face on the downstream side thereof seating againstsaid seat, the inner margin of said annular flow control device defininga straight-line flow orifice of less cross sectional area than the crosssectional area of the passageway through said seat and taperingoutwardly from the upstream to the downstream end thereof when said fiowcontrol device is in an unstressed condition, whereby an accuratecontrol of the flow through said flow orifice is attained at exceedinglylow pressure ranges as well as at high pressure ranges.

References Cited in the file of this patent UNITED STATES PATENTS2,454,929 Kempton Nov. 30, 1948 2,464,917 Babson Mar. 22, 1949 2,572,244Chase Oct. 23, 1951 2,728,355 Dahl Dec. 27, 1955 2,781,058 Warbus Feb.12, 1957

